Abstract:

Proposed is a luminaire (1), comprising light sources (10) and optical
elements (20). The light sources (10) are arranged in a first (11) and a
second array (12), while the optical elements (20) are arranged in a
first (21) and a second section (22). The first `light sources` array
(11) and the first Optical element` section (21) form a first group (31),
and the second array (12) and the section (22) form a second group (32).
The luminaire (1) is characterized in that the optical elements (20) of
each group are arranged to have different beam shaping characteristics,
and the arrays (11,12) are arranged to be individually addressable. This
is especially advantageous in illumination applications where the control
of the beam shape is required or desired. Advantageously, the invention
provides a luminaire (1) capable of adjusting the beam shape without
using an adjustable optical system. Moreover, the control bandwidth of
the light sources limits the speed with which the beam shape can be
adjusted.

Claims:

1. A luminaire comprising:a plurality of light sources and a plurality of
optical elements arranged in optical relationship to each other,the light
sources being arranged in a first array and a second array, the light
sources of the first array being controllable independently from the
light sources of the second array,the optical elements being arranged in
a first section and a second section, the optical elements in the first
section having different beam shaping characteristics from the optical
elements in the second section,the first array and the first section
forming a first group, andthe second array and the second section forming
a second group.

2. A luminaire according to claim 1, wherein the light sources of the
first array are interdispersed among the light sources of the second
array.

3. A luminaire according to claim 1, wherein at least one light source
array (11, 12) is arranged in a first sub-array capable of emitting light
of a first primary color and a second sub-array capable of emitting light
of a second primary color.

4. A luminaire according to claim 3, wherein the light sources of the
first sub-array are interdispersed among the light sources of the second
sub-array.

5. A luminaire according to claim 2, wherein the first array is arranged
to emit light of a first primary color and the second array is arranged
to emit light of a second primary color.

6. A luminaire according to claim 1, wherein the luminaire comprises a
light guide comprising a first facet arranged to couple light emitted by
the light sources into the light guide and a second facet arranged to
couple light out of the light guide.

7. A luminaire according to claim 6, wherein the plurality of the optical
elements are arranged to collimate the light emitted by the light
sources.

8. A luminaire according to claim 1, wherein the light sources are
selected from the group consisting of: inorganic LEDs, organic LEDs, and
semiconductor lasers.

9. (canceled)

Description:

FIELD OF THE INVENTION

[0001]The invention relates to a luminaire according to the preamble of
claim 1. The invention also relates to a beam shaping method according to
the preamble of claim 13. Such luminaires and beam shaping methods are
useful in illumination applications where the control of the beam shape
is required or desired.

BACKGROUND OF THE INVENTION

[0002]Luminaires capable of adjusting the shape of the emitted light beam
find their way in many applications. The beam shaping feature is highly
interesting, both in static as well as in dynamic applications.
Adjustable beam shapes in static application are normally implemented
through a number of preset modes, for instance `spotlight`, `floodlight`,
or `ambient light`. In applications using dynamic beam control, the beam
shape can normally be adjusted over a continuous range.

[0003]In conventional luminaires, the emitted light beam is created
through the use of a light source and an optical system. The optical
system usually is a reflector system but may also be a refractive system,
a diffractive system or a diffusive system. Adjusting the relative
position of the light source and the optical system classically controls
the beam shape. Taking a torch as an example, repositioning the light
bulb relative to the parabolic reflector (or the lens relative to the
light bulb) controls the shape--narrowly focused vs. wide flooding--of
the light beam. Applying switchable refractive elements--e.g. liquid
crystal lenses and electro wetting lenses--or switchable diffusers
constitute alternative well known technologies to adjust the beam shape
emitted by a luminaire.

[0004]A drawback of the prior art technology to adjust the beam shape of
the light emitted by a luminaire is the use of adjustable optical
systems, either through mechanical movement or electrical control. While
moveable systems are prone to wear and tear, electrically controllable
systems are usually highly complex and expensive. Furthermore, the
bandwidth of the mechanical moveable and electrically controllable
optical systems usually is limited to the frequencies with which the
optical system can be adjusted. Typically the bandwidth is 10-100 Hz for
mechanically moveable systems, up to 10 kHz for rotating systems, 100
kHz-1 MHZ for micromechanical systems (MEMS), and 50-1000 Hz for
electrically controllable systems.

SUMMARY OF THE INVENTION

[0005]It is an object of the present invention to provide a luminaire of
the kind set forth, capable of adjusting the light beam shape up to
extremely high frequencies. This object is achieved with the luminaire
according to the invention as defined in claim 1. According to a first
aspect, the invention is characterized in that the optical elements of
each group are arranged to have different beam shaping characteristics,
and the first light source array and second light source array are
arranged to be individually addressable. Advantageously, the invention
provides a luminaire that is capable of adjusting the beam shape without
the necessity of using an adjustable optical system. Moreover, the speed
with which the beam shape of the emitted light can be adjusted is now
limited to the control bandwidth of the light sources. In an embodiment
of the invention, the light sources are chosen from the group consisting
of inorganic LEDs, organic LEDs, and semiconductor lasers. The control
bandwidth of these light sources typically ranges from 1 MHz to 1 GHz.

[0006]In an embodiment the light sources of the first array are
interdispersed among the light sources of the second array. This
embodiment realizes advantageously different beam shapes having a common
centre of symmetry. Moreover, the first and second group will
consequently be interdispersed causing an observer not to recognize the
physical origin of for instance two different beam shapes.

[0007]In another embodiment at least one `light source` array is arranged
in a first sub-array capable of emitting light of a first primary color
and a second sub-array capable of emitting light of a second primary
color. In an embodiment, the light sources of the first sub-array are
interdispersed among the light sources of the second sub-array.
Advantageously, the color and the beam shape can be controlled and
adjusted independently from each other. In view of the fact that the
luminaire makes use of additive color mixing, the term `primary color`
has to be understood to comprise any color (i.e. spectrum) of light
emitted by the light sources in the luminaire. Thus `primary color` both
comprises a narrow bandwidth spectrum and consequently highly saturated
color as well as a large bandwidth spectrum and consequently unsaturated
color of light emitted. Hence, the scope of additively mixing `primary
colors` explicitly is not limited to f.i. highly saturated red, green &
blue light sources. On the contrary, the scope extends to mixing f.i.
warm-white and cool-white light sources.

[0008]In yet another embodiment according to the invention the first light
source array is arranged to emit light of a first primary color and the
second light source array is arranged to emit light of a second primary
color. Advantageously, both the color and the beam shape can be
controlled and adjusted simultaneously.

[0009]In an embodiment the luminaire comprises a light guide comprising a
first facet arranged to couple light emitted by the light sources into
the light guide and a second facet arranged to couple light out of the
light guide, advantageously enabling very thin luminaires. In an
embodiment the beam shaping characteristic of the optical elements are
arranged to collimate the light emitted by the light sources.
Advantageously, the light guide mixes the light originating from the
different light sources causing an observer not to recognize the
different physical origins of the light.

[0010]In an embodiment the indentations comprise side facets adapted to
reflect incident light rays. Advantageously, no light will be lost due to
absorption or scattering at the light sources, ensuring good light
efficiency.

[0011]In an embodiment the indentations are arranged in the plane of the
light guide in a stacked distribution. Advantageously the distance
between the stacked indentations controls the degree of light mixing
(resulting in for instance a more homogeneous colored beam when applying
multiple primary color light sources).

[0012]According to a second aspect, the invention provides a method for
controlling the light beam shape emitted by a luminaire in accordance
with the preamble of claim 13. The method is characterized by arranging
the optical elements of each group to have different beam shaping
characteristics, and arranging the first light source array and second
light source array to be individually addressable. Advantageously, the
invention provides a method for adjusting the beam shape of a luminaire
without the necessity of using an adjustable optical system. Moreover,
the speed with which the beam shape of the emitted light can be adjusted
is limited to the control bandwidth of the light sources.

[0013]These and other aspects of the invention will be apparent from and
elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]Further details, features and advantages of the invention are
disclosed in the following description of exemplary and preferred
embodiments in connection with the drawings.

[0015]FIG. 1 shows a front view of a luminaire according to the invention
including LEDs and lenses

[0016]FIG. 2 shows a light guide based luminaire according to the
invention

[0017]FIG. 3 shows a cross section through the light guide based luminaire

[0018]FIG. 4 shows a different configuration of the light guide based
luminaire

[0019]FIG. 5A shows a top view of another embodiment of a light guide
based luminaire, having a plurality of light sources arranged in a square
grid array

[0020]FIG. 5B shows a schematic cross-section view along a section
parallel to the luminaire in FIG. 5A illustrating the beam-shaping
properties of the rectangular in-coupling recesses

[0021]FIG. 5c shows a schematic cross-section view along a section
perpendicular to the luminaire in FIG. 5A illustrating an exemplary
beam-shaping structures for collimating light in a direction
perpendicular to the light-guide

[0022]FIG. 5D shows a schematic cross-section view along a section
perpendicular to the luminaire in FIG. 5A illustrating an exemplary
beam-shaping structures for collimating light in a direction
perpendicular to the light-guide

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023]FIG. 1 shows the front view of a luminaire 1 according to the
invention comprising a plurality of light sources 10 and optical elements
20 arranged in optical relationship to each other. The light sources 10
are indicated by the squares, triangles, and diamonds, while the optical
elements 20 are indicated by the full, dashed, and dotted circles. The
light sources 10 are arranged in at least a first array 11 and a second
array 12. Furthermore, the optical elements are arranged in at least a
first section 21 and a second section 22. The first light source array 11
and the first optical element section 22 form a first group 31.
Similarly, the second array 12 and second section 22 form a second group
32. To control the beam shape of the light emitted by the luminaire 1,
the optical elements 20 within the first group 31 (i.e. the first section
21) are arranged to have different beam shaping characteristics from
those in the second group 32 (i.e. the second section 22). Furthermore,
the light sources 10 in each group are arranged to be individually
addressable. That is to say, the first `light source` array 11 can be
controlled independent from the second `light source` array 12.

[0024]The advantage of this approach lies in the fact that the beam shape
of the light emitted by the luminaire 1 can now be adjusted by
controlling the individual `light source` arrays 11,12. Light sources 10
generally have a large control bandwidth (on-off, dimming). This
certainly holds for LEDs (inorganic and organic) and laser diodes, for
which the control bandwidth typically ranges from 1 MHz to 1 GHz.

[0025]In an embodiment of the invention all the light sources 10 emit the
same spectrum, which can range from a single saturated primary color
(RED, GREEN, BLUE, etc) to a full white spectrum. The characteristics of
the optical elements 20 in the different groups 31, 32 determine the beam
shape of the light emitted. For instance, consider a LED based luminaire
1 capable of switching between a `spot mode` and a `flood mode`. A highly
concentrated and focused light beam characterizes the `spot mode`; while
a wide spreading beam shape characterizes the `flood mode`. Assembling
for instance collimators in front of LEDs in the first group 31 (enabling
the `spot mode`) and diverging lenses in the second group 32 (enabling
the `flood mode`) realizes the switching capability of the luminaire 1.

[0026]Lenses, collimators, and diffusers may all function as optical
elements 20. As an example, the full circles in FIG. 1 may represent
positive lenses, the dashed circles negative lenses, and the dotted
circles collimators. The choice and beam shaping characteristics (such as
focal length, collimation angle, or scattering angle-influenced f.i.
through the size or shape of a scattering particle in the diffuser) of
the optical elements 20 may depend on the emission characteristics of the
light sources 10 and the luminaire 1 beam pattern desired. While LEDs
typically emit light with a large angular distribution (e.g. Lambertian),
laser diodes typically emit collimated light beams. Hence, groups 31,32
comprising LEDs and collimators/lenses on the one hand and groups
comprising of laser diodes and lenses/diffusers on the other hand yield
good results in practice.

[0027]Interdispersing the light sources 10 of the first array 11 among the
light sources 10 of the second array 12 will intrigue a layman observer
of a luminaire 1 according to the invention. Consequently, the first 31
and second group 32 will be interdispersed so that the observer will not
recognize the physical origin of the for instance the `spot and flood
modes`. From a technical standpoint, this embodiment realizes
advantageously different beam shapes having a common centre of symmetry.
Many tilings exist interdispersing two or more of the arrays, sections,
and groups. The choice of a particular tiling constitutes a design
consideration. Therefore, the scope of the invention covers any possible
tiling, whether symmetrical, asymmetrical, or quasi symmetrical.

[0028]In an embodiment, the light sources 10 emit light with different
spectra. Several configurations can be distinguished. In an embodiment of
the invention every light source 10 is capable of emitting a plurality of
primary colors. As an example, a LED package comprising for instance
three chips, where each chip (i) emits a primary color and (ii) is
individually addressable, functions satisfactorily. In another
embodiment, the light sources 10 emit only a single primary color.
Several arrangements exist for assembling such single color light sources
10 in the luminaire 1.

[0029]In one embodiment, the first `light source` array 11 is arranged to
emit light of a first primary color and the second `light source` array
12 is arranged to emit light of a second primary color. Combining each
array with optical elements 10 having different beam shaping
characteristics, to form the first 31 and second 32 group, has the
advantage of adjusting both the color and the beam shape simultaneously.
Hence, the luminaire 1 may switch from for instance a white `spot mode`
to a blue `flood mode`. Alternatively, applying both modes at the same
time may create desirable lighting effects in for instance a retail
environment. The white `spot mode` enables a customer to investigate the
object for sale in detail, while the colored `flood mode` creates an
ambient lighting enhancing the atmosphere and/or setting of the retail
environment (ranging from premium boutique to functional Do-It-Yourself).

[0030]In an embodiment of the invention the luminaire 1 comprises a light
guide 50 as shown in FIG. 2 (top view) and FIG. 3 (cross section). The
light guide 50 comprises at least one first facet 51 arranged to couple
light emitted by the light sources 10 into the light guide and at least
one second facet 52 arranged to couple light out of the light guide. The
light guide 50 comprises a transparent material, typically glass or a
plastic, guiding the light rays 15 and enabling the mixture of the light
rays of different primary colors or originating from individual light
sources 10. Applying side emitting LEDs as light sources 10 and
collimators as optical elements 20, advantageously enables very thin
luminaires 1 (typically with a thickness of 1-3 times the LED package
height, i.e. 1-5 mm for luminaires with a degree of collimation of
2×45 degrees beam width or wider). Mounting the LEDs on a PCB (not
shown) with two parallel layers of electrical connections allows for
their individual or group wise control. In an embodiment, indentations in
the light guide 50 allow for positioning the light sources 10 and the
optical elements 20. Advantageously, the optical elements 20 constitute
collimators to control the beam shape of the light emitted by the
luminaire 1. Collimation accommodates the anti-glare requirements for
luminaires 1, as these requirements prescribe that the light out-coupled
from the light guide 50 should not have too large angles of departure.
The indentations have a first facet 51 allowing the light emitted by the
LEDs to couple into the light guide 50. Furthermore, the indentations
have a second facet 52 for coupling the light out of the light guide.
Moreover, the indentations have side facets 53 adapted to reflect
incident light rays 15, f.i. through TIR or a coating.

[0031]FIG. 2 depicts a very simple tiling of the light sources 10 and
optical elements 20. For clarity reasons the Figure depicts the groups
31,32 with reference to only a limited number of light sources 10 and
optical elements 20. In fact, in this tiling the first group 31 comprises
the rows 201, 203, 205, and 207, while the second group 32 comprises the
rows 202, 204, 206. Many tilings exist, however, interdispersing two or
more of the arrays, sections, and groups. The choice of a particular
tiling constitutes only a design consideration. Hence, the scope of the
invention covers any possible tiling, whether symmetrical, asymmetrical,
or quasi symmetrical.

[0032]Advantageously, the light emitted by a first LED and entering the
light guide 50 through the accompanying indentation's first facet 51 will
not penetrate the indentation accommodating a second LED. Arranging the
indentations in the plane of the light guide in a stacked distribution,
with all first `incoupling` facets 51 oriented in one direction and all
second `outcoupling` facets 52 oriented in the opposing direction,
results in all the light rays 15 being reflected by either the side
facets 53 (through TIR) or the second facets 52. Advantageously, no light
will be lost due to absorption or scattering at the light sources 10,
ensuring good light efficiency. Advantageously the distance between the
stacked indentations controls the degree of light mixing (resulting in a
more homogeneous beam when applying multiple primary color light sources
10).

[0033]In another embodiment, at least one `light source` array 11, 12 is
arranged in a first sub-array 101 capable of emitting light of a first
primary color and a second sub-array 102 capable of emitting light of a
second primary color (FIGS. 1 & 4). Consequently, addressing the
individual sub-arrays 101, 102 in a single group 31, 32 enables adjusting
the color of a light beam emitted by the luminaire 1 without changing its
shape. Interdispersing the light sources 10 of the first sub-array 101
among the light sources 10 of the second sub-array 102, advantageously
enables a homogeneous color mixing in the light beam. Although FIG. 4
depicts this configuration for a light guide based luminaire 1, the scope
of the invention covers non-light guide based luminaires with this
configuration as well.

[0034]In FIG. 5A shows another embodiment of a luminaire 1, comprising a
light guide 50 and a plurality of light sources 10, here in the form of
omni-directional light emitting LEDs, located at corresponding
indentations/recesses having a square cross-section in the plane of the
light guide 50. The faces of the rectangular/square indentation form the
first `in-coupling` facets 51a-d (see FIG. 5B. Adjacent to each
indentation associated second `out-coupling` facets 52a-d are provided.
Each of these out-coupling portions comprises four regions a-d having
groove-shaped second `out-coupling` facets 52 extending in the directions
45°, 135°, 225°, and 315° with respect to the
centrally located indentation. The rectangular/square cross-section of
the indentation in the plane of the light guide 50, collimates the light
emitted by an uncollimated light-source 10, such as an omni-directional
LED, in the plane of the light guide 50 and thus splits it into four
separate light rays 15a-d along two orthogonal axes as schematically
indicated in FIG. 5A (only one light ray 15 is shown). This collimating
property of the indentation will be described in greater detail below in
connection with FIG. 5B.

[0035]As can be seen in FIG. 5A, the indentations are oriented in such a
way that the directions of the light rays 15 essentially coincide with
the directions of the second `out-coupling` facets 52 in the four regions
directly adjacent the indentation. Thus, a light ray 15 in-coupled into
the light guide 50 through the first `incoupling` facet 51, will
encounter either parallel grooves, which do not out-couple the light, or
perpendicularly oriented grooves, which do out-couple the light
(illustrated in the Figure for one light ray 15 only). The out-coupling
of light emitted by a particular light source 10 need not necessarily
take place in an out-coupling portion of the light guide associated with
another light-source, as is illustrated in FIG. 5A. Instead, the light
from a light source 10 can be out-coupled in the out-coupling portion
associated with that light-source following reflection so that the light
rays 15 emitted by the light-source change direction in the plane of the
light guide.

[0036]Turning now to FIG. 5B, the dimensioning of the rectangular
indentation/recess in FIG. 5A for achieving an acceptable degree of
collimation in the plane of the light guide 50 will be discussed. For a
point source, each of the four light rays 15a-d entering the first
`incoupling` facets 51a-d is collimated (in air) within 2×45
degrees. For a finite source, however, the length D of the incoupling
facets 51a-d (assuming a square cross-section) of the indentation should
be about 2.5 times the light source 10 diameter d, in order to produce a
cut-off angle Θ.sub.cut-off of 60 degrees, as schematically
illustrated in FIG. 5B (important to minimize glare by light leaving the
luminaire 1 at angles >60 degrees.) In order to achieve a collimation
in the plane of the light guide 50 which is narrower than 2×45
degrees, additional optical elements 20, such as conventional collimator
funnels are required.

[0037]With reference to FIGS. 5C&D, two exemplary optical elements 20 for
achieving collimation in a direction perpendicular to the light guide 50
will be briefly described. In FIG. 5c, a side-emitting LED package 10 is
shown, including a collimating TIR (total internal reflection) optical
element 20 inserted in the in-coupling indentation in the light guide 50.
Light emitted by the LED is coupled into the TIR optical element 20 at an
in-coupling face thereof and then, through the geometry of the TIR
element internally reflected to be emitted as a light ray 15 (here only
shown in one direction) which is collimated in a direction perpendicular
to the light guide 50 and to enter the light guide 50 through the first
`incoupling` facet 51. FIG. 5D schematically illustrates another
exemplary collimator 20 in the form of a reflective funnel which
redirects light emitted by the light source (LED) 10 as indicated by the
light ray 15 drawn in FIG. 5D entering the light guide 50 through the
first `incoupling` facet 51.

[0038]Although the invention has been elucidated with reference to the
embodiments described above, it will be evident that alternative
embodiments may be used to achieve the same objective. The scope of the
invention is therefore not limited to the luminaire described above, but
can also be applied to any other light emitting device where it is
desired to control the beam shape of the light emitted such as, for
example, automotive headlamps and theatre spotlights. Moreover, many
possible modifications fall within the scope of the invention. For
example, the collimation means in the light guide 50 described above may
be combined in various ways. Furthermore not every indentation
necessarily needs to accommodate a light source 10 and an optical element
20 combination. Some indentations may for example be used for outcoupling
light only. Furthermore the indentations need not necessarily be arranged
as individual isolated structures. For example, the scope of the
invention covers arranging the indentation as a linear array of parallel
grooves--thus creating a prism faced zig-zag surface where the `zig`
provides a first `incoupling` facet 51 and the `zag` a second
`outcoupling` facet 52. Alternatively, the light sources 10 and optical
elements 20 may all be located at one side edge of the light guide 50.